Cyclotron and annihilation lines in γ-ray bursts

Venera 11 and Venera 12 have detected emission and absorption lines in the energy spectra of many γ-ray bursts. The similarity between the spectral features observed during different events reveals the similarity in physical conditions and processes which occur within the burst sources. These lines are the most convincing evidence that the γ-burst sources contain neutron stars with a strong magnetic field. We present here results of a comprehensive analysis that included weaker bursts, which indicate that the presence of lines in the γ-burst spectra, in particular of absorption lines in the region 30–70 keV is a characteristic rather than an exceptional feature.